Rationalist epistemology – rene descartes

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Rationalist epistemology – rene descartes

  1. 1. Rationalist Epistemology – Rene Descartes Unit 2, Part 2
  2. 2. Rene Descartes (1596-1650) <ul><li>A contemporary of Galileo and Kepler </li></ul><ul><li>Discovered analytic geometry </li></ul><ul><li>Found himself in the midst of an era absorbed in the religion/science opposition </li></ul><ul><li>Sought to write a book of philosophy that would foster reconciliation between science and religion </li></ul>
  3. 3. The Foundation of Knowledge <ul><li>Descartes sets out to find the foundation of knowledge </li></ul><ul><li>To do so, he utilizes methodological doubt </li></ul><ul><ul><ul><li>Requires the doubting of any proposition if there is even the slightest reason to do so </li></ul></ul></ul><ul><li>What’s the point? </li></ul><ul><ul><ul><li>To find something that cannot be doubted…this absolutely certain principle will be the foundation of knowledge </li></ul></ul></ul>
  4. 4. Can we trust our senses? Look at the picture on the left. Are those lines straight or sloped? If you think they look sloped – you agree with nearly all those who look at this photo. But you’d be wrong – those lines are actually straight. Your eyes have deceived you! Look at the picture on the left. Can you count the black dots? How many are there? The answer is zero! Your eyes made you see black dots where there are none. You’ve been tricked!
  5. 5. Can we trust our senses? <ul><li>As we have just witnessed, our senses can deceive us. </li></ul><ul><ul><ul><li>But there is another argument against sensory experience as the foundation of knowledge </li></ul></ul></ul><ul><ul><ul><li>“ I remind myself that on many occasions I have in sleep been deceived by similar illusions, and in dwelling carefully on this reflection I see so manifestly that there are no certain indications by which we may clearly distinguish wakefulness from sleep that I am lost in astonishment.” Rene Descartes, Meditations on First Philosophy </li></ul></ul></ul><ul><li>How do you know you aren’t just dreaming now? </li></ul><ul><ul><ul><li>The conclusion is there is no philosophical proof that at any given moment you are not dreaming </li></ul></ul></ul><ul><li>Therefore, the senses cannot be the foundation of knowledge </li></ul>
  6. 6. Is Mathematics a sound foundation? <ul><li>Mathematics is made up of a priori truths, such as 1+1=2 </li></ul><ul><ul><ul><li>It would seem that this could serve as a firm foundation for knowledge. After all, Plato considered mathematics to be true knowledge, albeit not the highest form of knowing. </li></ul></ul></ul><ul><li>However, Descartes asks of us, how do we know that the universe was not created by an evil demon, whose deepest desire is to deceive us, even in the most basic of truths? </li></ul><ul><ul><ul><li>This is Descartes’ “Evil Genius” hypothesis </li></ul></ul></ul>
  7. 7. Descartes’ “Evil Genius” <ul><li>Suppose that rather than an honest, merciful God who created the world (as Christians believe), the world was instead created by an evil daemon, whose sole focus was to frustrate and deceive humanity. Could we then trust mathematics? How could we KNOW that 1+1=2? </li></ul><ul><li>Descartes concludes that if an evil genius were to be the creator of the world, we cannot know that 1+1=2. Doubt, in regards to mathematics, is therefore possible. </li></ul>
  8. 8. Where does that leave us? <ul><li>Descartes has successfully eliminated sensory experiences and mathematics from the foundation of knowledge. Is there anything left? </li></ul>
  9. 9. The Cogito <ul><li>Yes! Descartes has finally reached the first principle; the foundation upon which knowledge rests </li></ul><ul><li>He concludes, Cogito ergo sum, “I think, therefore I am” </li></ul><ul><ul><ul><li>In the very act of thinking, we prove that our minds exist. We can still doubt the body (remember, Descartes’ doubt of sensation and sense experiences), but our minds are necessarily extant at the time we begin to think or doubt </li></ul></ul></ul><ul><ul><ul><li>This is the foundation upon which Descartes’ then rebuilds the world </li></ul></ul></ul>

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